Staphylococcus aureus occupies a dominant position in external diseases of the eye. Little is known about the relationship of this organism to the external eye, and the host response to it. Our studies have shown that immunization with the cell wall of S. aureus and more specifically with the ribitol teichoic acid which it contains is associated with the development of hypersensitivity lesions of the cornea. Moreover, antibody rather than delayed hpersensitivity to ribitol teichoic acid appears to be involved in the immunopathogenesis of these lesions. The specific aims of our proposed grant include the following: 1) Passive transfer of phlyctenulosis. We will attempt to transfer phlyctenulosis from one inbred animal to another using gamma globulin or lymphocytes from immunized animals. 2) Role of necrotizing toxin in the production of hypersensitivity lesions of the cornea. Necrotizing toxin has been regarded as the principal mechanism by which S. aureus attacks the eye. To determine if necrotizing toxin plays an important local role in the production of hypersensitivity lesions of the cornea, imumnized rabbits will be challenged topically with either a strain of S. aureus that produces necrotizing toxin or a strain of S. aureus that does not. 3) Development of enzyme-linked immunosorbent assay for measuring antibodies to ribitol teichoic acid. Ths extremely sensitive test will be used to measure antibody to ribitol teichoic acid in rabbit tears as well as in the serum and tears of patients with phlyctenules, catarrhal infiltrates and blepharitis related to S. aureus. 4) Role of S. epidermidis in hypersensitivity diseases of the external eye. We wish to determine if hypersensitivity to S. epidermidis cell wall and the glycerol teichoic acid it contains can be associated with inflammation of the external eye. 5) Development of rabbit model of staphylococcal blepharitis. We have preliminary data suggesting that hypersensitivity to S. aureus may play an important role in the development of staphylococcal blepharitis. This model of staphyloccal blepharitis will be developed and explored.